Molecular-Squeeze Triggers Guest Desorption from Sponge-Like Macrocycle Crystals

Desorption in conventional porous sorbents often employ external forces including inert gas blowing, heating, vacuum treatment to trigger guest release. We here report an unprecedented molecular-squeeze triggered guest release behavior from sponge-like macrocycle crystals. The crystals function as typical sponge to include guest molecules within their microscopic voids that are adaptively formed, thus acting as adsorbents for toluene/pyridine separations. Intriguingly, vaporized ethyl acetate (EA) molecules trigger the guest release from the crystals without entering the pores or voids of the crystals to replace the guests. Instead, they work as external forces applied directly onto the crystals themselves, ''squeezing" the materials to close the voids through supramolecular interactions between EA and macrocycles on the crystal surface and release the guest molecules. Various experimental techniques as well as molecular dynamics simulations reveal the mechanism of the molecular-squeeze induced guest release procedure. The EA-regenerated crystals can be recycled multiple times without the loss of separation performance. Compared with conventional guest release procedure, this method is manipulated in a mild condition, showing the potential in saving cost and energy.